Python - subtraction inside rolling window

Question

I need to make subtractions inside red frames as [20-10,60-40,100-70] that results in [10,20,30]

Current code makes subtractions but I don't know how to define red frames

seq = [10, 20, 40, 60, 70, 100]
window_size = 2
for i in range(len(seq) - window_size+1):
    x=seq[i: i + window_size]
    y=x[1]-x[0]
    print(y)

Answer 1

You can build a quick solution using the fact that seq[0::2] will give you every other element of seq starting at zero. So you can compute seq[1::2] - seq[0::2] to get this result.

Without using any packages you could do:

seq = [10, 20, 40, 60, 70, 100]
sub_seq = [0]*(len(seq)//2)
for i in range(len(sub_seq)):
    sub_seq[i] = seq[1::2][i] - seq[0::2][i]

print(sub_seq)

Instead you could use Numpy. Using the numpy array object you can subtract the arrays rather than explicitly looping:

import numpy as np
seq = np.array([10, 20, 40, 60, 70, 100])
sub_seq = seq[1::2] - seq[0::2]

print(sub_seq)